The airlines are raising fares to cover higher jet fuel prices, which are more than $3 a gallon, behind only 2008, when oil prices surged.

Delta Air Lines touched off the latest fare hike by adding up to $20 to the price of domestic round-trips bought on short notice. American Airlines choose a more modest increase of $10, but applied it to virtually all tickets. By midday Thursday, Delta, United, Continental and US Airways had all matched American. None of the low-cost airlines — including Southwest, JetBlue and AirTran — had raised prices, said Rick Seaney, CEO of FareCompare.com.